MIXING FERTILIZERS ON THE FAKM 51 



60. Commercial fertilizers are used for the nitrogen, phos- 

 phoric acid, and potash they contain. Nitrogen is obtained 

 chiefly from nitrate of soda, dried blood, dried fish scrap, 

 and cottonseed meal. Phosphoric acid is obtained from 

 ground bone, basic slag, ground phosphate rock, and acid 

 phosphate. Potash is obtained from muriate of potash, 

 sulphate* of potash, and kainite. 



61. Fertilizer materials are about as follows : Chilean 

 nitrate of soda, 15% ; acid phosphate, 16% ; and muriate 

 of potash, 50%. 



The prices of these materials are subject to market changes, 

 but are usually about as follows : nitrate of soda, 30 per 

 pound in 200-pound bags ; muriate of potash, 30 per pound 

 in 200-pound bags ; and acid phosphate, 10 per pound in 

 125-pound bags. 



62. A complete fertilizer (one containing all the ingredi- 

 ents) is quite often unnecessary and expensive. A crop of 

 clover or other legumes may supply the soil with all the 

 nitrogen needed for the next crop. In this case phosphoric 

 acid and potash are the only fertilizing elements necessary. 



A farmer can make at home 100 Ib. of 2-8-4 fertilizer 



1 



from nitrate of soda containing 15 % of nitrogen, acid phos- 

 phate containing 16% of phosphoric acid, and muriate of 

 potash containing 50% of potash as follows : 



The mixture must contain 2% nitrogen, 8% phosphoric acid, and 

 4% potash. 



2% of 100 Ib. = 2 Ib., amount of nitrogen required. 



8% of 100 Ib. = 8 Ib., the amount of phosphoric acid required. 



4% of 100 Ib. = 4 Ib., the amount of potash required. 



(1) Since only 15% of the nitrate of soda is nitrogen, the 2 Ib. of 

 nitrogen is 15% of the amount of nitrate of soda required for the mix- 

 ture, or 13 J Ib. of nitrate of soda. 



(2) Since only 16% of the acid phosphate is phosphoric acid, the 8 Ib. 

 of phosphoric acid is 16% of the amount of acid phosphate required 

 for the mixture, or 50 Ib. of acid phosphate. 



